Engineering Wonders of the World
Volume I

322 ENGINEERING WONDERS OF THE WORLD. r—.6»o-----t N ■bSOH-'.-.-t-lMn-T Under the north span is seen a vessel of the relative size of the Lusitania. S Queensferry . Tower N. Queensferry Fife Tower ELEVATION OF THE FORTH BRIDGE, SHOWING PRINCIPAL MEASUREMENTS. science of the time, this proposition began and ended on paper. Thirteen years later Mr. James Anderson of Edin- burgh came along with plans and elevations, all complete, for a bridge at the same site. His designs show three sus- of 2,000 feet each—and also, Barren Schemes for Tunnelling— The Final Scheme. Bridge Com- for erection And Bridging the Forth. pension spans we would venture to suggest, considerable ignorance of the problems which he had set himself to solve, as the whole structure was not to include more than 2,500 tons of iron. If his scheme had reached the construction stage, it would beyond doubt have afforded an excellent, if disastrous, example of “ how not to do it.” Passing over the abortive scheme of the North British Railway in 1860 to throw an arched bridge over the river five miles west of the Queensferries, we come to that of 1873, which is coupled with the name of Sir Thomas Bouch. This engineer, at the request of the Forth Bridge The need for a bridge remaining impera- tive, Messrs. Fowler and Baker, the eminent firm of engineers, were called upon for other designs. They submitted drawings for a cantilever bridge of enormous and quite unprecedented size ; and these having been approved by the pany, Parliamentary powers were sought and obtained in 1882. As a result of the engineers’ ability we now enjoy the use of the mammoth steel structure which efficiently and gracefully, if not beau- tifully, spans the Forth, and bids fair to span it for many years to come, given freedom from earthquakes and hostile dynamite. Since the reader may possibly boggle over stated that a The ordinary Sir Thomas Bouch’s Designs. Meaning of “ Cantilever.” the term “ cantilever,” be it cantilever means a bracket, balcony is a cantilever of a kind. Imagine a large plank laid from a balcony at one side of a street to a balcony on the other side, and you have a partial representation of the principle of the Forth Company, backed by the Great Northern, Bridge. We say partial, because it was essen- North Eastern, Midland, and North British Railway Companies, drew out four native specifications for a suspension to be erected between North and Queensferry. The design authorized Parliamentary Act had main towers 550 feet high, and spans of 1,600 feet. Work had been actually begun when the collapse of the Tay Bridge, in December 1879, caused the promoters to reconsider the whole matter, and abandon Bouch’s design. alter- bridge South by a out one the tial that the cantilevers should be built in pairs from central towers to balance another as they grew. We will now dissect the dimensions of bridge, so as to get a grasp of the magnitude of the task of building it. The supports are three towers, each 342 feet high, reckoning from the top of the four piers on which each stands. A tower is com- posed of four enormous vertical tubes. 12 feet Dimensions of the Bridge.